This invention relates to an ink cartridge for supplying ink to a head of a record apparatus.
Patent Document 1 proposes attaching a sensor comprising a piezoelectric vibrator to a side of an ink container so that the piezoelectric vibrator is contactable with ink. The detection is made as to whether or not ink exists above the piezoelectric vibrator, based on the difference between residual vibration when the piezoelectric vibrator comes in contact with ink and that when the piezoelectric vibrator is exposed to the atmosphere.
Since an air bubble has an intermediate characteristic between liquid and the atmosphere, the residual characteristic of the piezoelectric vibrator becomes unstable, causing a detection mistake.
To solve such a problem, Patent Document 2 discloses placing a wall extending in a horizontal direction in an area in which a liquid level sensor is accommodated for preventing an air bubble from coming in direct contact with the liquid level sensor.
Patent Document 1: JP-A-2001-328278
Patent Document 2: European Patent Application Publication No. 1053877 page 42 paragraph 320, FIG. 79
However, ink has a component containing a surface active agent, etc., and thus if a large amount of ink is consumed in a record head as an image is printed, etc., an air bubble occurs because of the atmosphere entered through an atmospheric communication hole, causing a large amount of bubbles accumulated to adhere onto the sensor. Since a bubble has an intermediate characteristic between liquid and the atmosphere, the residual characteristic of the piezoelectric vibrator becomes unstable, causing an ink level detection mistake.
It is therefore an object of the invention to provide an ink cartridge for making it possible to prevent a detection mistake caused by adhesion of a bubble caused by an air bubble occurring in ink, to thereby stably detect the ink level or ink amount.
To the end, according to the invention as claimed in claim 1, there is provided an ink cartridge comprising: a container having at least one ink chamber storing ink therein; a partition wall disposed in the container, and defining a sensor accommodation area in a part of the ink chamber, the partition wall further defining an upper gap and a lower gap through which the sensor accommodation area is in fluid communication with another part of the ink chamber; and a liquid level sensor comprising a piezoelectric element, which is disposed in the sensor accommodation area. The upper gap blocks entry of a bubble as it is into the accommodation area, and enlarges and destroys the bubble if the bubble is pushed out into the accommodation area from the upper gap.
Because of the configuration, before the flow force of a bubble exceeds the limit of the capillary force produced by the upper gap, if the bubble accumulates in the upper part in the ink chamber, it does not pass through the upper gap of the partition wall and is prevented from flowing into the sensor accommodation area. If the number of bubbles in the vicinity of the liquid surface increases and the flow force of the bubbles exceeds the limit of the capillary force of the gap, the bubbles moves from the gap to the inside of the sensor accommodation area while they are enlarged. In this process, the bubbles are destroyed. Therefore, the bubble is prevented from entering the sensor periphery and being collected at the sensor periphery, and erroneous detection of the liquid level by the piezoelectric element forming a part of the liquid level sensor is prevented.
In the invention as claimed in claim 4, a plurality of the partition walls are disposed to be separated one from another in a horizontal direction. Therefore, entry of the air bubble into the sensor accommodation area can be more positively prevented.
In the invention as claimed in claim 5, the partition wall is disposed so that a part of the accommodation area in the vicinity of the upper gap is spread and enlarged toward the liquid level sensor. Therefore, the bubble is easily expanded and then destroyed when the bubble passes through the upper gap.
In the invention as claimed in claim 6, the upper gap is set to a dimension of 0.5 mm to 1 mm, so that the bubble accumulated in the upper part in the cartridge main body is prevented from directly moving to the sensor accommodation area and if the bubble moves to the sensor accommodation area, it is swollen and is reliably destroyed.
In the invention as claimed in claim 11, the distance between the upper gap of the partition wall and the liquid level sensor is set to 8 mm or more, so that the bubble can be destroyed before it adheres to the sensor.
The present disclosure relates to the subject matter contained in Japanese patent application No. P2001-359232 (filed on Nov. 26, 2001) and P2002-305861 (filed on Oct. 21, 2002), which are expressly incorporated herein by reference in their entireties.